main thing I look for is ease of access. sharp lips on the inside that will lacerate your wrist are sadly all too common. Work out what mobo you are getting before you pick the case so you know where you'll need to route cables and you can check out if they'd be easily accessible otherwise you'll curse the choose 2 years later when you're trying to upgrade something. Will you be air cooling? If so, worth working out what kind of flow you'll get by checking out where fan holes are located compared to the main components on your rig.